Particle Accelerators/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim pulls his stick back and hits the cue ball. It flies into the triangle of billiard balls and bounces off, without budging them at all. TIM: Huh. What are the chances of that? Next to Tim, Moby is holding a bottle of "Glue-On" brand glue behind his back. He hands Tim a letter. Tim reads from a typed letter. TIM: Dear Tim and Moby: I know an atom's nucleus is made of protons and neutrons, but what are those things made of? Sincerely, Jason. Good question! Physicists used to think those particles were fundamental. MOBY: Beep? TIM: That means they can't be split up into anything else. In theory, a fundamental particle is as small as matter gets. Early scientists thought elements like gold and oxygen were fundamental. An animation shows a Middle Eastern scientist examining a yellow lump of gold with a magnifying lens. TIM: Then an English chemist John Dalton came along and demonstrated that elements must be made of atoms. An animation shows John Dalton in front of a large yellow piece of gold. The camera zooms into the gold until its individual atoms are visible. Dalton points to one of the atoms with a wooden pointer. TIM: A century later, it was shown that atoms had a nucleus of protons and neutrons, orbited by electrons. The animation zooms further into one of the gold atoms, showing the subatomic particles Tim describes. TIM: For a while, scientists were pretty sure that that was as far as it went. Until they became aware of some visitors from outer space: cosmic rays. MOBY: Beep? An image shows a "Superb Woman" comic book cover showing the superhero Superb Woman being hit by laser rays. A speech bubble next to Superb Woman reads, "Oh no! Cosmic rays!" TIM: Uh, no… most cosmic rays aren't actually "rays" at all. A disappointed Moby is holding the "Superb Woman" comic book in his hand. TIM: They're mainly protons, electrons, and other particles, propelled by the explosions of distant stars. Some of them come from our own sun. Space is filled with these particles, zipping around near the speed of light! And Earth is constantly bombarded by them. In the 1930s, scientists began studying the collisions between these rays and ordinary matter. An animation shows a particle speeding along against a backdrop of stars. The animation zooms out to show the particle, along with many others, flying out of the Sun and into the Earth's atmosphere. TIM: When a cosmic ray collided with an atom's nucleus, it created showers of tiny particles that nobody could identify. This was major. It suggested that maybe protons and neutrons weren't fundamental; they could be broken up into smaller pieces! But catching one of these collisions wasn't easy. An animation shows a cosmic ray shooting into an atom and striking the nucleus. It explodes into a shower of much smaller particles, many following spiral paths. TIM: You had to wait around for a cosmic ray to hit a tiny target. Which could take a while. An animation shows a scientist in a white lab coat standing on top of a mountain next to a wooden table with an odd-looking machine made out wood, metal, and glass on it. He checks his watch and the scene changes to show he has a beard and is noticeably older. He raises his hand as a light bulb appears over his head. TIM: So, researchers started designing machines that would create cosmic rays on demand. MOBY: Beep? TIM: They'd start by isolating a proton. An animation shows one electron circling a nucleus containing one proton. A hand appears and flicks the electron away. TIM: It carries a positive electric charge. So it's repelled by other positive charges, and attracted to negative charges. An animation shows the single isolated proton moving forward in a long skinny tube from a positively charged end to a negatively charged end. A stream of protons follows the first proton. TIM: And if it's moving, it reacts the same way to north and south magnetic fields. That means you can use magnetic and electric fields to move the proton, and direct it towards a target. And voila, you've built a cosmic ray gun, better known as a particle accelerator. The animation zooms out to show a north pole magnet on top of the tube, and a south pole magnet on the bottom. The animation zooms out of the diagram to show that it's the inside of a handheld proton gun being held by a Ghostuster??. TIM: You could steer your particles in a straight line to build a linear accelerator, or LINAC… Along a spiral path, to build a cyclotron...Or a circular path, inside a synchrotron. A three-way split screen shows animated diagrams of the linear path of particles in a linear accelerator, the spiral path in a cyclotron, and the circular path in a synchrotron. TIM: But early models couldn't get near the speed of a cosmic ray. An animation zooms into the LINAC diagram. It is slowly firing particles at a large atomic nucleus but the particles are bouncing off of the nucleus instead of breaking it apart. TIM: So the collisions weren't strong enough to break up the particles they were studying. MOBY: Beep? TIM: To get the speeds they required, scientists had to think big. An animation shows a scientist in a lab coat holding a clipboard and standing next to a tabletop LINAC connected to a large battery with alligator clips and wires. TIM: After all, they were trying to replicate the power of an exploding star! Billions of volts of electricity would be needed to propel the particles. And more distance was required to build up the necessary speed. An animation shows the scientist imagining a much bigger accelerator humming with electricity with a "Danger High Voltage" sign in front of it. The scientist looks very small standing in front of the giant accelerator. The animation pans to the right to show the long tube of the linear accelerator, and follows the length of the tube far into the distance of a long tunnel. TIM: Synchrotrons were increased to dozens of feet in diameter. For LINAC's, it meant extending their length to hundreds, even thousands, of feet. The Stanford Linear Accelerator, built in 1962, is almost two miles long! An image shows an aerial view of the expansive Stanford Linear Accelerator positioned on a grassy field and surrounded by buildings and trees. TIM: These new machines were powerful enough to crack open protons and neutrons. But making sense of the results was another challenge entirely. An animation shows a particle ray hitting an atom and splitting its nucleus, with particles exploding into much smaller particles and flying off into all directions. MOBY: Beep? TIM: When particles collide at near-light speeds, they don't just destroy each other. They create new particles, with totally different properties! The animation of the particle ray hitting the atom and splitting its nucleus is repeated, but this time the shower of exploding particles is shown as following many spiral paths. TIM: It'd be like if you loaded a pool ball into one cannon…And I loaded one into another…And we fired them directly at each other. They smash into each other in mid-air, exploding into a cloud of dust. Plus… a baseball, a beach ball, and a golf ball. An animation shows Moby on a hilltop dropping a ball down the barrel an old-fashioned cannon facing to the right. The animation changes to show Tim lighting the wick of a left-facing cannon on another hilltop. The cannons fire at the same time. A split screen shows each ball racing through the air. The split disappears and the screen merges into one shot just before they collide in a cloud of dust. A baseball, a beach ball, and a golf ball pop out of the dust and bounce away. TIM: It seems crazy to us, but physicists weren't entirely surprised. It just confirmed what Albert Einstein theorized in 1903: That energy can change into matter. An animation shows Albert Einstein catching the beach ball that fell from the sky in the palm of his hand and tossing it up and down. A speech bubble above him appears that reads, "E = mc2". The animation zooms out to show Einstein dressed in casual beach attire sitting on a rock on a sandy beach at the edge of the ocean. TIM: You need lots of energy packed into a small space for it to happen. Which is what you get when particles collide at near-light speeds. MOBY: Beep?! TIM: All of this stuff is way too small to see with a microscope. So researchers had to build new kinds of detectors. The first were boxes filled with special liquids and gases. An animation shows spiral streaks emanating from a central point inside of rectangular, clear-glass chamber. TIM: When particles collided inside, the debris would leave behind streaks of bubbles or clouds. Most detectors today work on the same principle, but use electronic sensors instead. An animation shows a modern digital display of colored streaks on a black background. TIM: Studying the trails can tell you a lot: the particle's mass… how energetic it is… whether it has a charge…It's kind of like a footprint: the same particle will always leave the same kind of trail behind it. An image shows a yearbook photo of a particle path inside a chamber. The label below the photo reads "K+". The animation pans to the right to show the yearbook photo of another streak path. The label below it reads "Pi -". TIM: By the late 1960s, more than 150 fundamental particles had been detected! This did not make physicists happy. The animation zooms out to show an entire two-page spread full of such streak photos, with the title "Particle Zoo" at the top. The pages flip, revealing multiple pages of particles. The books is slammed shut by a scientist sitting at his office desk and looking unhappy. MOBY: Beep? TIM: The basic laws of nature tend to be elegant and simple. Like if all matter could be boiled down to three ingredients: protons, neutrons, and electrons. 150 ingredients, on the other hand, was a clue that we had something wrong. An image shows an old fashioned cookbook opened to the page showing the recipe for Ordinary Matter, with the ingredients listed as protons, neurons, and electrons. A hand points to the ingredients, as many more ingredients are added to the list, including Pion, Sigma, Tau neutrino, Preon, Majoron, Positron, Muon, Photon, Tachyon, Axion, and Antineutrino . TIM: Finally, American physicist Murray Gell-Mann had an idea: Most of the new particles weren't fundamental, and neither were protons and neutrons. They were made of smaller particles, which Gell-Mann called quarks and gluons. Protons and neutrons were composed of these particles, too. An animation shows the unhappy scientist from before back at his desk, spraying a potted plant with water. He puts his finger to his face, deep in thought, as the animation zooms in on a water droplet that he sprayed on his plant. A water molecule is shown as being composed of protons and neutrons, and the protons and neutrons are shown as being composed of the much smaller particles, quarks and gluons. TIM: There was no evidence for this claim - but the math worked out beautifully. About ten years later, quarks were produced in two different accelerators. They behaved exactly as Gell-Mann had predicted. The image of the aerial view of the Stanford Linear Accelerator is shown again. An animation shows quarks behaving in their characteristic ways. MOBY: Beep! TIM: Yeah, it may seem like Gell-Mann just invented quarks out of thin air. But the reasoning he used is how a lot of scientific advances are made. An animation shows a scientist in a lab coat pouring a test tube full of colored liquid into a potted plant. The plant wilts, and the scientist looks unhappy. The animation changes to show the scientist holding out the plant in front of another scientist in a classroom. A light bulb appears over the second scientist's head as the two discuss. The animation changes back to the first scientist in the plant room pouring a test tube full of a different colored liquid into the wilted plant. It blooms. TIM: Experimenters collect data from nature, and not all of it makes sense. Thinkers like Gell-Mann puzzle over these mysteries. They try to adjust the theory to fit the observations. Then experimenters look for evidence to support those new ideas. This kind of back-and-forth has given us the Standard Model: the scientific theory that describes atomic particles and how they behave. An image shows a diagram of the particles in the Standard Model, divided into the categories quarks, leptons, guage bosons, and scalar bosons. TIM: Like all theories, the model is a work in progress. We're constantly testing it in accelerators and the latest generation of particle colliders. In these machines, two particle beams travel in opposite directions. When they reach sufficient speed, the beams are focused at the same point. An animation shows a circle-within-a-circle diagram of a particle collider. A particle beam in the inner circle is traveling in the opposite direction of a particle beam in the outer circle. A split screen shows two particles traveling in opposite directions toward one another. The split between them disappears, the particles collide at the point at which they are both focused, and an explosion is created. TIM:The energy released creates conditions similar to just after the Big Bang... The animation zooms into the explosion to reveal a plasma "soup" of energy and particles moving in spiral paths. TIM: When the universe was so hot, there were no atoms, just a soup of energy and particles. We can get a glimpse of this period by studying the data from colliders. The biggest one, the Large Hadron Collider in Switzerland, is 5 miles across! An animation shows the digital screen of a particle collider showing colored streaks of particle collision data. The screen changes to show an image of Tim and Moby standing under a portion of the Large Hadron Collider wearing construction safety hats. TIM: Here's Moby and me standing near one of its massive detectors. In 2012, scientists there found the Higgs boson, a fundamental particle predicted way back in the 1960s. The image showing the diagram of the particles in the Standard Model, divided into the categories quarks, leptons, guage bosons, and scalar bosons, is shown again. MOBY: Beep! TIM: You're all about the practical stuff, huh? Well for your information, all this expensive research has done a lot of good. An animation shows the tunnel containing the long linear collider tube. TIM: Besides expanding what we know of the universe, particle accelerators are used in medical imaging…Cancer treatments…Computer chip making…And dozens of other applications. A split screen shows an image of a PET scan, radiation treatment, and a computer chip. TIM: Anyway, it's your break. Back at the pool table, Tim hands the stick to Moby, who lines it up with the cue ball, and draws his arm back. He forcefully slams the stick into the ball, but the ball doesn't budge. The stick vibrates violently, which makes Moby vibrate violently, and his whole body shakes along the floor and off-screen. Tim is shown holding the bottle of Glue-On glue behind his back. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts